Borrowings (Long Term Debt) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Notes and subordinated debt	$ 574,161,000	$ 544,806,000
Debt issuance cost on senior fixed-rates	(2,829,000)	(3,030,000)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	346,841,000	317,486,000
Long-term debt	$ 570,029,000	$ 540,364,000
Variable interest rate	3.25%	4.85%
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.95%
Long-term Debt [Member]
Debt Instrument [Line Items]
Discount on senior fixed-rate notes	$ (1,303,000)	$ (1,412,000)
Junior subordinated debt Webster Statutory Trust I floating-rate notes due September 17, 2033 [Member]
Debt Instrument [Line Items]
Notes and subordinated debt	$ 77,320,000	77,320,000
Debt Instrument, Redemption, Period One [Member] \| 4.375% Senior fixed-rate notes due February 15, 2024 [Member]
Debt Instrument [Line Items]
Senior notes, interest rate (as a percent)	4.375%
Notes and subordinated debt	$ 150,000,000	150,000,000
Debt Instrument, Redemption, Period Two [Member] \| 4.375% Senior fixed-rate notes due February 15, 2024 [Member]
Debt Instrument [Line Items]
Senior notes, interest rate (as a percent)	4.10%
Notes and subordinated debt	$ 346,841,000	317,486,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 46,841,000	$ 17,486,000

Face (par) amount of debt instrument at time of issuance.

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